Fan muffler



Dec. 23, 1941. GEVRENZ 2,267,275 I FAN MUFF-LER I Filed Nov. 25,- 1939 '2 Sheets-Sheet 1 I I v I6 g- 53" .57 \zy f J I N VENTO R FOEE/FT A. GEVRENZ ATTORNEY Dec. 23, 1941. RFA. GEVRENZ FAN MUFFLER Filed Nov. 25, 1939 2 Sheets-Sheet 2 (INVENTOR RaBERr A. [if VRENZ ATTORNEY Patented Dec. 23, 1941 FAN MUFFLER Robert A. Gevrenz, Brooklyn, N. Y., assignor, by

mesne assignments, to General Machine Company, Inc., New York, N. Y., a corporation of New York Application November 25, 1939, Serial No. 306,050

10 Claims.

This invention relates to a mufiier for eliminating substantially all of the noises produced by incoming gas, such as air in a fan operated blower. In numerous fields it is desirable to use a blower for supplying a stream of air or other gas under forced draft. This is particularly true in the stoker art wherein blowers are employed in conjunction with a coal feeding means for supplying a forced draft to the fuel in a furnace in accordance with the rate at which fuel is fed into the furnace.

In installations of this character, it is frequently desirable to regulate or vary the amount of air supplied to the furnace by a damper or other suitable control placed in the outlet of the blower. This creates a back pressure inside the blower and around the fan when the damper is partly closed, resulting in an objectionable hum and other noises at the blower inlet. In various other blower applications, back pressure producing an objectionable noise may be developed even though no damper is used in the blower outlet.

One object of my invention is to provide a mufiler for the intake of such a fan which is simple to construct and which eliminates substantially all of the noises produced by incoming gas.

A further object of my invention is to break up the gas entering a blower into a number of small streams and to provide one or more pockets in which the incoming gas is allowed to mix quietly with any gas forced back by reason of back pressure on the blower.

The invention is illustrated by a blower for use in connection with a stoker to supply air under forced draft to fuel inside a furnace, such as shown and described in the Hall et al. Patent #21)? 7,882. It will be understood, however, that the invention has other applications than in the form illustrated and is applicable to blowers used for other purposes than the one indicated.

In the embodiment of my invention illustrated in the drawings Figure 1 is a vertical sectional View on the line l-I of Figure 2 through approximately the center of a blower equipped with a'muiiler in accordance with my invention.

Figure 2 is a side elevation of the-blower and muflier as viewed from the left side of Figure 1 with portions of the mufiier broken away to show the interior construction.

In the drawings, numeral 5 designates a suitable base on which a motor 6 is mounted to drive a centrifugal fan 7 within a fan housing 8. The

fan housing 8 also may be mounted on the frame 5 and held in place by the bolt 9 and nut I0. The fan or blower housing 8 may be conveniently cast in two parts, the section II consisting of an annular disk-shaped plate provided with a small opening l2 for the shaft l3 of motor 6 and having a number of suitable lugs l4 provided with openings and spaced around the outer edge of the housing.

The other section l5 of the fan housing 8 may consist of a plate of complemental shape having a central opening l6, considerably larger than the opening [2 in section II, and an integral arcuate mufile housing wall I! extending at right angles to the main portion of the plate. Suitable lugs l8 may also be provided around the outer edge of this portion l5 of the fan housing so that the two halves of the housing may be secured together by the bolts IS. The fan housing thus provides a generally circular narrow opening 2B within which the fan 1 may rotate.

The fan i may be secured to the motor shaft 83 by means of a set screw 2| or other suitable means. The blades 22 of the fan I may be of any suitable construction adapted to throw the air outwardly toward the outer portion of the housing.

The two halves II and I5 of the fan housing are preferably flared outwardly at their periphery through an are extending nearly 130 to provide the outlet conduit portion 23 of the housing through which gas is delivered from the blower. This outlet conduit portion 23 may be terminated by a collar 24 capable of receiving and holding one end of a suitable tube 25 or other conduit.

In the use of such a blower in connection with a stoker to supply air under forced draft, I prefer to employ a butterfly valve 26 mounted in the tube 25 to throttle the amount of air supplied to the stoker when necessary. The motor 6 may have a shaft which extends through the motor, as shown at 21, and is thereby adapted to be connected to and to drive other parts of the stoker mechanism (not shown), as well as the fan 1.

The arcuate mufile housing wall I! preferably extends approximately three-quarters of the Way around the inlet side of the fan housing 8 and is provided with a ledge 28 to receive the perforated diaphragm 29 and to hold it in a tilted position with respect to the fan housing 8. is preferably inclined so that the diaphragm 29 is positioned closest to the fan housing 8 at a point midway between the ends of the wall I]. Ledge 28 may be extended across the space between the ends of wall I! by a raised section 30 integral with the fan housing. At intervals The ledge 28 around the arcuate wall l1, threaded openings 3| may be tapped to receive bolts 32 which hold the diaphragm 33 in place as a circular cover plate covering the space within the arcuate wall I1.

Diaphragm 29 is preferably provided with a plurality of perforations 34, most of which are formed in the diaphragm at a point remote from the opening between the ends of arcuate wall I1. Diaphragm 33 is preferably provided with a stud 35 secured thereto by a rivet 36 or other suitable means and having a rubber tip 31 adapted to press against the diaphragm 29 and hold it in place. This also serves to render the diaphragm 29 and cover plate 33 more rigid and prevents vibration thereof.

In the operation of the device illustrated embodying my invention, the gas, such as air, to be handled by the blower, flows in between the ends of the arcuate wall I! until it reaches the perforations as in diaphragm 23. The air then passes through the perforations 34 into th space between diaphragm 29 and the fan housing section l5 and flows back into the inlet opening l8 in the fan housing. After the air passes through the inlet Iii, it is forced by the fan blades 22 outwardly and around the fan housing until it leaves by way of the conduit portion 23 in the pipe 25 in the usual manner.

The mufile housing and diaphragm or baffle 29 provide a tortuous passage for the air entering the fan housing and breaks up the incoming air into a number of small streams. Thus, when a considerable back pressure is caused by closing or partially closing of the damper 26, or by some other means, the incoming air is allowed to mix quietly with air driven back by the back pressure in the pockets formed between the diaphragm 29 and the housing section [5. By this simple ex.- pedient, it is possible to eliminate substantially all of the objectionable hum and other noises that are ordinarily produced when back pressure is created in a blower.

It is not necessary in accordance with my in vention to use sound deadening devices because my invention eliminates the cause of noises at their source and does not simply try to deaden the sound of such noises. The muffer device according to this invention is relatively inexpensive and easy to construct, portions of it being readily formed integrally with a fan housing of any conventional construction. Many variations in the construction illustrated are possible, however, and my invention is not limited to the specific form of fan. mufiler illustrated in the. drawings.

The tilting of the diaphragm or bafiie 23 as illustrated is preferred primarily because of the compactness and the simplification of manufacture and assembly that is accomplished by this arrangement. If the'diaphragm should not be tilted, however, an opening of sufficient siz between diaphragms 29 and 33 would have to be provided and this might require a mufile housing substantially thicker and more bulky than would be needed with the diaphragm 29 in the tilted position.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope ofthe invention claimed.

Iclaim:

1. In a blower for creating a stream of gas under pressure, an outlet for said gas, an inlet for said gas, and a baflie having a plurality of relatively small openings at only one side thereof arranged to cause the gas to flow through a tortuous passageway and through said openings in order to reach said blower inlet.

2. A blower comprising a fan housing, an outlet and inlet therefor, means for throttling the flow of gas from said outlet, a housing around said inlet of substantially greater size than. said inlet, and baffle means for directing the flow of gas entering said blower through a tortuous passageway within said inlet housing, said bafile means and fan housing being constructed and arranged to form a dead end pocket therebetween of sufficient volume to allow incoming gas to mix quietly with gas forced back by said throttling means.

3. A blower comprising a fan housing, an outlet and inlet therefor, means for throttling the flow of gas expelled through said outlet, a housing around said inlet of substantially greater size than said inlet and having an opening offset laterally from said inlet, and baffle means having localized perforations for directing the flow of gas entering said blower through a tortuous passageway within said inlet housing, the unperforated portion of said baffle means and said fan housing being constructed and arranged to form a pocket therebetween.

l. A blower comprising a fan housing having an outlet and a centrally located inlet, a muffle housing around said inlet and of substantially greater size than the inlet, and a baffle within said housing extending transversely of said inlet and substantially completely across said muffle housing, said baffle having a plurality of perforations laterally offset from said inlet on only one side thereof so that gas entering the inlet is directed through a tortuous passageway and broken up into a number of small streams, the unperforated portion of said baffle being spaced from said fan housing to form a pocket therebetween.

5. A blower comprising a fan housing having an outlet and a centrally located inlet, means for throttling the flow of gas expelled through said outlet, a muffle housing around said inlet and of substantially greater size than the inlet, and a bafile within said housing extending transversely of said inlet and substantially completely across said muffle housing, said baflie having a plurality of perforations at only one side of said inlet so that gas entering the inlet is directed through a tortuous passageway and broken up into a number of small streams.

6. A blower comprising a fan housing having an outlet and a centrally located inlet, a muflle housing wall extending around the inlet but open at one side and formed integral with at least a portion of said fan housing, means secured to said wall to complete the muffle housing, and a baffle disposed substantially completely across said muffle housing so that gas entering at the open side of said wall is directed across the muffle housing before returning to the fan inlet on the other side of said ballle.

7. In a blower having a centrally located inlet, a muille housing surroundingsaid inlet and having an opening at one side thereof, and a fixed bafiie within said housing extending between said opening and inlet to form a tortuous passageway for gas passing from said opening to said inlet, said baflle'being inclined at an acute angle to said blower with the portion thereof adjacent said opening nearest said blower.

8. In a blower having a centrally located inlet, a mufiie housing surrounding said inlet and having an opening ofiset laterally from said inlet, and a baille within said housing extending between said opening and inlet with a plurality of perforations therein disposed a substantial distance from said opening, said baffie being inclined at an acute angle to the blower with the imperforate portion nearest said blower.

9. Apparatus as defined in claim 8 in which at least a portion of the muffle housing is formed integrally with the blower.

10. Apparatus as defined in claim 8 in which a removable portion of the muflie housing serves to hold the bafiie in place.

ROBERT A. GEVRENZ. 

